Garage door opener with instant reverse mechanism

ABSTRACT

An electrical operator assembly for garage doors and the like includes a reversible electric motor, a belt member and means deflecting the belt member from a straight line path. When the door operated by the assembly encounters an obstruction, the belt member overcomes the deflecting pressure and operates reversing switch means to reverse the direction of operation of the electric motor. The control circuitry includes a multiposition relay adapted to reverse the direction of operation of the motor upon change of the contacts closed therein when a signal is received from the reversing switch which transmits its signal directly to the relay. In addition, a disabling switch is directly responsive to operation of the drive means after a preselected period of travel in one direction to disable the reversing switch and prevent its transmission of a signal to the motor when the door approaches the end of its preselected period of travel in that direction. The motor remains in closed circuit contact with the relay means during reversal of direction by the reversing switch.

United States Patent 91 Geoffrey 3,764,874 o'er. 9, 1973 GARAGE DOOR OPENER WITH INSTANT REVERSE MECHANISM Primary ExaminerBernard A. Gilheany Assistant Examiner-W. E. Duncanson, Jr. Attorney-Peter L. Costas [57] ABSTRACT An electrical operator assembly for garage doors and the like includes a reversible electric motor, a belt member and means deflecting the belt member from a straight line path. When the door operated by the assembly encounters an obstruction, the belt member overcomes the deflecting pressure and operates reversing switch means to reverse the direction of operation of the electric motor. The control circuitry includes a multiposition relay adapted to reverse the direction of operation of the motor upon change of the contacts closed therein when a signal is received from the reversing switch which transmits its signal directly to the relay. In addition, a disabling switch is directly responsive to operation of the drive means after a preselected period of travel in one direction to disable the reversing switch and prevent its transmission of a signal to the motor when the door approaches the end of its preselected period of travel in that direction. The motor remains in closed circuit contact with the relay means during reversal of direction by the reversing switch.

7 Claims, 7 Drawing Figures PATENTEUUBT ems SHEET 2 OF 2 FIG.6

FIG-5 //30 LIGHT DELAY CIRCUIT GARAGE DOOR OPENER WITI-I INSTANT REVERSE MECHANISM BACKGROUND OF THE INVENTION Electrically operated door units are conventionally employed for moving garage doors between open and closed positions in response to a signal from a manual switch or from a radio transmitter. Generally, such door operators employ reversible electric motors and it is customary for them to employ some form of adjustable limit switches to discontinue flow of current to the motor when the door has reached either preselected extreme in its path of travel.

Generally such operators include clutches of some type to allow slippage of the motor when an excessive strain is placed thereon, particularly if some obstruction is encountered or if an excessive weight is inadvertently placed upon the door. In some instances, operation of such clutch means will result in termination of current flow but the pressure for the door to move in the given direction continues to the level required to effect clutch slippage.

In some door operators, reversing mechanisms are provided which will automatically reverse the direction of door operation in the event that an obstruction is encountered. In this manner, injury to persons or goods may be avoided. Frequently these automatic reversing mechanisms tend to be unduly sensitive and cause spurious reversal of door operation and even recycling from one position to another. In other instances, the reversing mechanism does not readily permit precise control of door operation so that reversal may occur inadvertently as the door reaches either extreme of travel. This is particularly a problem when snow, ice, leaves and the like tend to accumulate at the bottom the door track to a level sufficient to produce spurious or unwanted operation of the reversing mechanism.

It is an object of the present invention to provide an electrical operator assembly for garage doors and the like of novel construction which is relatively simple and economical to fabricate and which will effect substantially instantaneous reversal of the door movement upon the encountering of an obstruction of predetermined size.

It is also an object to provide such a door assembly in which the sensitivity of the reversing mechanism may be adjusted readily and its point of disablement may also be adjusted conveniently depending upon the desired tolerance to minor obstructions at the end of movement of the door.

Another object is to provide such door assembly employing a simple lever action which is readily and economically manufactured and assembled and which is relatively trouble-free and long-lasting in operation.

Still another object is to provide such a door assembly in which the number of electrical components is minimized and those components are relatively simple and long-lived in construction to ensure extended periods of trouble-free operation for the electrical circuitry.

SUMMARY OF THE INVENTION It has now been found that the foregoing and related objects can be readily attained in an electrical operator assembly for garage doors and the like which includes a support, a reversible electric motor mounted on the support and a belt member mounted for rotation on the support in either direction of rotation of the motor. Drive means interconnects the motor and the belt member to effect its rotation in either direction, thus enabling movement of the door between open and closed positions. The belt member extends about the drive means to define a substantially U-shaped portion with spaced legs to opposite sides of the drive means.

There is provided means for deflecting a leg portion of the belt member from a straight line path towards the opposite leg and that deflecting means includes an elongated deflecting member pivoted at one end on the support and having its opposite end portion slidably engaged with the belt member and spring means biasing the opposite end portion of the deflecting member to produce the deflection. The belt member is adapted to overcome the biasing force of the biasing means upon movement over the deflecting member towards the pivoted end thereof and the encountering of an obstruction by the door during operation and it will pivot away from the opposite leg of the belt member and return to a substantially straight line path. The biasing means is closely adjustable to control the biasing force required to be overcome by the belt member to effect movement of the belt member to a straight line path. This movement of the belt member overcoming the biasing force of the biasing means will act upon reversing switch means operable to generate a signal.

The control circuitry for the motor includes limit switch means responsive to operation of and directly actuated by the drive means to discontinue operation of the motor after a preselected period of travel of the belt member in either direction of rotation. Disabling switch means is directly actuated by the drive means after movement thereof for a preselected period of travel of the belt member in one direction, and this preselected period of travel is less than the preselected period of travel for the motor discontinuing limit switch means in that direction. Multiposition relay means controls current flow to the motor to reverse the direction of operation thereof upon change of the contacts closed therein. The signal from the reversing switch means is transmitted directly to the relay to change its position and the contacts closed therein and thereby change the direction of rotation of the motor upon the encountering of an obstruction by the door. The motor remains in closed circuit contact with the relay means during reversal of direction effected by operation of the reversing switch means. The disabling switch means opens the circuit for the reversing switch means to prevent generation of a signal thereby to the relay means when the drive means approaches the end of its preselected period of travel in the one direction, thus avoiding unwanted operation.

In its most usual form, the relay means comprises a two-position relay having a member moveable between the two positions, a solenoid coil, and an armature acted upon by the solenoid coil to drive the moveable member from one position to the other. The moveable member is latched in its position until moved therefrom by action of the solenoid. The motor is a reversible motor having two windings and the contacts of said relay in the two positions thereof are each connected directly to one of the windings whereby the direction of rotation of the motor may be altered by changing the position of said relay.

Preferably, the circuit includes means connecting the two windings of the motor to supply current out of phase to the winding of the motor which is not directly receiving current through the contact of the relay in the then operative position thereof. The limit switch means in the control circuitry comprises separate limit switches disposed in the circuits between the separate windings of the motor and the contacts of the relay in the two positions thereof, whereby opening of either of the limit switches in the operative or closed circuit will discontinue flow of current to the motor and terminate operation of the assembly.

The biasing means is adjustable to control the biasing force required to be overcome by the belt member to effect operation of the reversing switch. This is conveniently effected by use of deflecting means comprising an elongated member pivoted at one end on the support and biasing means comprising a compression spring acting upon the opposite end of the elongated member to bias the opposite end toward the belt member. The elongated member acts upon the reversing switch means when it overcomes the biasing force.

The disabling switch means and the reversing switch means are in series with current flow to the reversing switch being through the disabling switch in its normally closed position. In this manner, disabling switch means is opened to disable the reversing switch means.

BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS FIG. 1 is a perspective view ofa door operator assembly embodying the present invention;

FIG. 2 is a bottom perspective view of the motor end of the assembly of FIG. 1 with the housing removed and with the boom and chain assembly fragmentarily illustrated;

FIG. 3 is a fragmentary plan view to an enlarged scale of the boom, endless chain and reversing mechanism components of the assembly;

FIG. 4 is a fragmentary perspective view of the pressure bar and reversing switch mechanism to a greatly enlarged scale and with the adjusting knob removed for clarity of illustration;

FIG. 5 is a fragmentary end elevational view of the pulley end of the assembly with the housing removed and with portions of the components broken away for clarity of illustration and with one nut shown in phantom line at the opposite extreme of the path of travel;

FIG. 6 is a fragmentary sectional view along the line 6 6 of FIG. 5; and

FIG. 7 is a partially schematic wiring diagram for the electrical circuitry of the door operating assembly.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Turning now in detail to FIG. 1 of the attached drawings, a garage door operator assembly embodying the present invention includes an elongated channelshaped boom member generally designated by the numeral l0 and a housing generally designated by the numeral 12 having a body portion 14 and an end closure portion 16 releasably engaged therewith by the latch 18. The connecting arm generally designated by the numeral 20 extends downwardly from the channel of the boom and is engaged in its upper end in the carrier 22; its other end has a coupling arm 24 for engagement in a pivot bracket (not shown) on the garage door (not shown). In accordance with conventional practice, this assembly is suspended in the garage or other area by straps (not shown) or the like.

As is seen in FIGS. 2 and 3, the carrier 22 is mounted on sprocket chain portion 26 of an endless drive member generally designated by the numeral 28 and which also has a cable portion 30. The endless drive member 28 is disposed within the channel of the boom member 10 and at one end (the left as viewed in FIGS. 1 3) has its chain portion 26 in driving engagement with the sprocket gear 32 and its other end extends about a pulley or idler roller (not shown) in the channel of the boom member 10 at a point remote from the housing 12. As seen in FIG. 2, the housing 12 encloses a mounting plate 34 upon the upper surface of which the one end of the boom member 10 is secured and upon the lower surface of which are mounted a reversible electric motor 36 with a drive shaft 38, an electrical component module 40 and the shaft generally designated by the numeral 42.

At its lower end the rotatably mounted shaft 42 has mounted thereon the clutch pulley 44 and at its upper end the sprocket gear 32 is mounted so that driving engagement is provided thereby. The shaft 38 of the motor 36 has a motor pulley 46 thereon and the belt 48 provides driving engagement between it and the clutch pulley 44 in either direction of rotation of the motor and thus movement of the endless drive member 28 and carrier 22 in either direction along the length of the boom member 10.

Above the housing plate 34, a notch 50 extends through the portion of the sidewall 52 and into the adjacent portion of the top wall 54 of the boom member 10. The sidewall 52 is also provided with a vertically extending slot 56 at a point spaced therefrom towards the sprocket gear 32 and an aperture 58 at a point spaced therefrom away from the sprocket gear 32. Pivotably seated in the slot 58 is the tongue 60 at one end of the elongated pressure bar generally designated by the numeral 62. At its other end the pressure bar 62 has a longitudinally extending notch 64 in which is slidably seated the shank 66 of the fastener 68 which extends through and is seated in the aperture 58. Mounted on the shank of the fastener 68 outwardly of the bar 62 are a compression spring 70 and an adjustment knob 72.

The pressure bar 62 has an arm 74 which extends inwardly through the notch 50 in the sidewall 52 and bears against the chain portion 26 so as to deflect that portion inwardly from a straight line path under the action of the compression spring 70, and the biasing pressure may be adjusted by rotation of the adjusting knob 72 on the threaded shank 66 of the fastener 68.

The outer surface of the free end of the pivoted pressure bar 62 will bear upon the elongated upstanding activator arm 76 or the reversing limit switch generally designated by the numeral 78 when it is pivoted outwardly from the sidewall 52 in the direction indicated by the arrow A in FIG. 4 by pressure exerted by the chain portion 26 and sufficient to overcome the biasing pressure of the compression spring 70. As best seen in FIGS. 1 and 2, the limit switch 78 is mounted on the bottom of the mounting plate 34 and has its actuator arm 76 extending upwardly through a cutout 80 therein. The actuator arm 76 will press against the switch bottom 82 when the pressure bar 62 pivots sufficiently, thereby sending an impulse to the control mechanism.

Turning now to FIGS. 5 and 6, the mechanism for limiting operation or travel of the endless drive member or belt 28 is illustrated. The shaft 42 is rotatably mounted in the bushings 84, 86 in the bracket 88 and has a threaded intermediate portion 90 upon which are threadably mounted a pair of nuts 92, 94 having a mu]- tiplicity of radially extending arms 96, 98. The bracket 88 also supports an elongated spring stop member 100 which is releasably engaged in the spacing between arms 96, 98 so as to prevent rotation thereof.

When the motor 36 operates, the rotation of the shaft 42 will cause the trapped nuts 92, 94 to move upwardly and downwardly along the threaded portion 90 since they are prevented from rotating by the stop member 100. As they move one direction or another, one of the nuts 92, 94 will deflect one of the actuator arms 102, 104 of the limit switches 106, 108 to open the circuit, thus stopping operation of the motor 36 and movement of the endless drive member 28 and carrier 22. When the nut 92 moves to the right as seen in FIG. 5 during movement of the door, it will strike the actuator arm 102 to open switch 106 although it also moves the actuator arm 104 of the switch 108. Shortly before it acts upon the actuator arm 102 sufflciently to open the switch 106, it will first act upon the actuator arm 110 of the disabling limit switch 112 to open that switch and disable the reversing circuit components.

Similarly, when the motor is reversed, the nut 94 will travel along the threaded portion 90 until it strikes the actuator arm 104 at the end of opening movement of the door, thus opening switch 108. In this direction of movement, the disabling switch 112 is closed throughout the cycle. It will be appreciated that the extent of travel of the nuts 92, 94 may be adjusted by springing the stop member 100 outwardly from the arms 96, 98 sufficiently to permit rotation of the nuts 92, 94 along the length of the threaded portion 90.

In normal operation of the door operator assembly, current flowing to the motor 36 will cause the carrier 22 to move along the boom in one direction or the other with the chain portion 26 distorted from a straight line path by the biasing, pressure of the compression spring 70 acting upon the pivoted pressure bar 62. If an obstruction is encountered, this will produce tensioning of the endless drive member 28 and the chain portion 26 will strive to overcome the biasing pressure of the spring 70 and straighten itself out into a straight line path. If this tensioning is sufficient to reach or exceed the value established by adjustment of the biasing pressure through the adjustment knob 72, the actuator arm 76 will be moved against the switch button 82 to close the reversing switch 78 and send an impulse to the control circuitry for the motor 36 which will reverse its direction of operation, all as will be described hereinafter in detail.

Turning now to FIG. 7, the electrical circuitry of the present embodiment may be more readily understood. As shown the motor 36 has two windings 150, 152 so that altering the phase of current flow to the windings 150, 152 will alter the direction of rotation of the shaft 38 and thus the direction of movement of the carrier 22 along the boom member 10. To prevent injury to the motor 36, a thermal overload circuit protection device 154 is incorporated.

The path of current to the windings 150, 152 of the motor 36 is controlled by the multipole relay 139 which has contacts 144 and 146 respectively in line with the windings 150 and 152 through the normally closed limit switches 106 and 108. Current flowing through either line to one of the windings 150, 152 will be directed by the capacitor 148 to the other of the windings out of phase. The relay clapper 142 is operated by the armature 141 in response to current flowing in the coil 140 which will move the clapper 142 to the opposite position where it will latch until another impulse occurs in the coil 140. Whenever the door operator assembly receives a start signal from the manual switch or radio receiver (both not shown) generally designated by the switch 79, current is already flowing through the circuitry 120, 122 and through the windings 126, 128 of the transformer generally designated by the numeral 124 to the terminal 134 of the terminal box. The closing of switch 79 energizes the relay coil 140 to operate the clapper 142 and close the circuit to the motor 136 through one of the limit switches 106, 108. Current also is provided directly to the light delay circuit schematically designated by the numeral 130 which controls the lamp 132.

As seen, the reversing switch 78 is in series with the disabling switch 112, through the terminal contacts 136, 138. The disabling switch 112 is normally closed so as to allow current to flow through the line to the normally open reversing switch 78, whereby closing of the reversing switch 78 by tensioning of the chain portion 26 sufficient to overcome the biasing pressure of the compression spring 70 will cause an electrical impulse to travel to the relay coil 140 and move the clapper 142 to the other of the contacts 144, 146. This in turn will reverse the direction of current flow to windings 150, 152 of the motor 36, thus reversing the direction of motor operation and door movement.

However, during closing movement of the door, the nut 92 will strike the actuator arm of the disabling switch 112 shortly before the limit of its downward travel and open the switch 112, thus terminating current flow to the reversing switch 78 through the terminal 138. As a result, snow or other small obstructions under the door which might produce tensioning of the chain portion 26 will not cause reversing of the current flow and opening movement of the door. The distance of travel during which the reversing switch 78 is disabled may be readily varied by changing the actuator arm 110 or by substituting a different switch.

As the door reaches its limit of travel in either direction, the nut 92 will move the actuator arm 102, 104 of the appropriate limit switch 106, 108 to open that switch. This will open the circuit and terminate current flow to the windings 150, 152 of the motor 36. However current continues to flow to the light delay circuit and thence to the lamp 132 for the desired period of time. When the next start impulse is received from the manual button, radio receiver or the like 79, the impulse transmitted to the coil of the relay 139 through the start circuitry (not shown) will move the clapper 142 to the other of the contacts 144, 146, the limit switch 106, 108 of which is closed to permit current to flow directly to the respective winding 150, 152 of the motor 36 and cause its operation in the reverse direction. As the motor operates, the limit switch 106, 108 opened by the action of the nut 92, 94 will return to its normally closed position. When the movement is in the opening direction, the nut 92 will move away from the actuator arm 110 of the disabling switch 112 to allow it to return to its normally closed position and return the reversing switch 79 to operating condition.

In the illustrated embodiment the chain tensioning will normally function only in closing movement of the door so that the pressure bar will function to operate the reversing switch only during such closing movement. It will be appreciated that the chain biasing mechanism amy be duplicated or modified so as to permit operation of the reversing switch during opening movement of the door as well as during closing movement.

It will be appreciated that the limit switches employed in the present invention may vary from those specifically illustrated and that the circuitry may also vary from that specifically employed herein with proper modification of the several components. However, the illustrated circuitry is extremely advantageous in requiring a limited number of components which are relatively inexpensive and readily serviced.

in adjusting the reversing mechanism, the door operated by the assembly is raised to its open position by a suitable signal to the assembly. An obstruction such as a chair or basket is placed within the door opening and a signal is transmitted to cause the mechanism to drive the door in the closing direction. If the door reverses upon contact with the obstruction, the biasing pressure provided by the compression spring is correctly adjusted. If, however, the door automatically reverses or cycles back and forth prior to contacting the obstruction, the adjusting knob should be turned to move it inwardly on the fastener and thereby increase the compression of the spring; such adjustments should be made in small increments to avoid ovecorrection. Conversely, if the door remains in contact with the obstruction, the adjusting knob should be turned to decrease the compression of the spring, again in small increments to avoid overcorrection.

Normally, the disabling switch actuator arm should be set so as to operate that switch about 1 4, or even up to 6, inches before the door reaches the end of its closing movement. In this manner, small amounts of snow, leaves or the like will not cause reversing of the door mechanism even though the chain may be tensioned in the course of completing its closing movement.

It will be appreciated that the length of travel of the nuts upon the lead screw may be readily adjusted for varying heights of doors. Most conveniently, the limit switch for discontinuing current flow to the motor in either extreme of travel and the disabling limit switch are mounted upon a common support plate.

Thus, it can be seen that the operating assembly of the present invention provides a substantially instantaneously acting reverse mechanism in the event that an obstruction is encountered. The sensitivity of the reversing mechanism may be adjusted readily and its point of disablement may also be adjusted readily depending upon the desired tolerance to minor obstructions at the end of closing movement of the door. The lever action for operating the reversing mechanism is relatively simple and economical to manufacture and assemble, and is relatively trouble free and long lasting in operation. The number of electrical components is minimized and these components are relatively simple long lived switches and relays to assure extended periods of trouble free operation.

Having thus described the invention, I claim:

1. In an electrical operator assembly for doors and the like, the combination comprising:

a. a support;

b. a reversible electric motor on said support;

c. a belt member mounted for rotation on said support in either direction of rotation;

d. drive means on said support interconnecting said motor and said belt member to effect rotation thereof in either direction, said belt member extending about said drive means to define a substantially U-shaped portion with spaced legs to opposite sides of said drive means;

e. means deflecting a leg portion of said belt member from a straight line path towards the opposite leg and including an elongated deflecting member pivoted at one end on said support and having its opposite end portion slidably engaged with said belt member and spring means biasing said opposite end portion of said deflecting member towards said belt member, said belt member being adapted to overcome the biasing force of said biasing means upon movement over said deflecting member towards the pivoted end thereof and the encountering of an obstruction by the associated door operated thereby to return to a substantially straight line path to pivot the elongated deflecting member away from said opposite leg of said belt member, said biasing means being closely adjustable to control the biasing force required to be overcome by said belt member to effect movement of said belt member to a straight line path;

f. reversing switch means engageable by said deflecting member upon pivoting thereof and operable to generate a signal upon overcoming of the biasing force of said biasing means; and

. control circuitry for said motor including:

1. limit switch means responsive to operation of and directly actuated by said drive means to discontinue operation of said motor after a preselected period of travel of said belt member in either direction of rotation;

2. disabling switch means directly actuated by said said drive means after movement thereof for a preselected period of travel in one direction, said preselected period of travel being less than the preselected period of travel for the motor discontinuing limit switch means in that direction; and

3. multiposition relay means controlling current flow to said motor to reverse the direction of operation thereof upon change of the contacts closed therein, said reversing switch means sending an electrical signal directly to said relay to change the contacts closed therein and thereby change the direction of rotation of said motor upon the encountering of an obstruction by the associated door, said motor remaining in closed circuit contact with said relay means during reversal of direction by operation of said reversing switch means, said disabling switch means opening the circuit for said reversing switch means to prevent generation of a signal thereby to said relay means when said drive means approaches the end of its preselected period of travel in said one direction.

2. The electrical operator assembly of claim 1 wherein said relay means comprises a two-position relay having a member moveable between said two positions, a solenoid coil, and an armature acted upon by said solenoid coil to move said moveable member from one position to the other, said moveable member being latched in position until moved therefrom by action of said solenoid, and wherein said motor comprises a reversible motor having two windings and wherein the contacts of said relay in said positions thereof are each connected directly to one of said coils whereby the direction of rotation of said motor may be varied by changing the position of said relay, and wherein there is included means connecting said two windings of said motor to supply current 90 out of phase to the winding of said motor not directly receiving current through the contact of the relay in the operative position thereof.

3. The electrical operator assembly of claim 2 wherein said limit switch means in said control circuitry comprises separate limit switches disposed in the circuits between the separate coils of said motor and said contacts of said relay in the two positions thereof, whereby opening of either of the limit switches in the closed circuit will discontinue flow of current to said motor and terminate operation of the assembly.

4. The electrical operator assembly of claim 1 wherein said biasing means comprises a compression spring acting upon the opposite end portion thereof to bias said opposite end portion toward said belt member and threaded adjusting means to closely adjust the biasing force exerted thereby.

5. The electrical operator assembly of claim 1 wherein said disabling switch means and said reversing switch means are in series with current flow to said reversing switch being through the disabling switch in its normally closed position, said disabling switch means opening to disable said reversing switch means.

6. The electrical operator assembly of claim 1 wherein said drive means includes a shaft member having a threaded portion and a threaded member mounted thereon, said support including means to prevent rotation of said threaded member whereby rotation of said shaft will produce movement of said threaded member along the length thereof; and wherein said limit switch means is actuated by said threaded member during movement thereof to a preselected distance along the length of said threaded portion, wherein said limit switch means comprises a pair of limit switches, and wherein there are provided a pair of threaded members at spaced points along the length of said threaded portion each acting upon one of said pair of limit switches at either extreme of the preselected period of travel.

7. The electrical operator assembly of claim 6 wherein said pair of limit switches and said disabling switch are mounted adjacent each other and each has an actuator arm, one of said threaded members acting upon the actuator arm of said disabling switch means shortly before acting upon the actuator arm of the limit switch in the same direction of travel. 

1. In an electrical operator assembly for doors and the like, the combination comprising: a. a support; b. a reversible electric motor on said support; c. a belt member mounted for rotation on said support in either direction of rotation; d. drive means on said support interconnecting said motor and said belt member to effect rotation thereof in either direction, said belt member extending about said drive means to define a substantially U-shaped portion with spaced legs to opposite sides of said drive means; e. means deflecting a leg portion of said belt member from a straight line path towards the opposite leg and including an elongated deflecting member pivoted at one end on said support and having its opposite end portion slidably engaged with said belt member and spring means biasing said opposite end portion of said deflecting member towards said belt member, said belt member being adapted to overcome the biasing force of said biasing means upon movement over said deflecting member towards the pivoted end thereof and the encountering of an obstruction by the associated door operated thereby to return to a substantially straight line path to pivot the elongated deflecting member away from said opposite leg of said belt member, said biasing means being closely adjustable to control the biasing force required to be overcome by said belt member to effect movement of said belt member to a straight line path; f. reversing switch means engageable by said deflecting member upon pivoting thereof and operable to generate a signal upon overcoming of the biasing force of said biasing means; and g. control circuitry for said motor including:
 1. limit switch means responsive to operation of and directly actuated by said drive means to discontinue operation of said motor after a preselected period of travel of said belt member in either direction of rotation;
 2. disabling switch means directly actuated by said said drive means after movement thereof for a preselected period of travel in one direction, said preselected period of travel being less than the preselected period of travel for the motor discontinuing limit switch means in that direction; and
 3. multiposition relay means controlling current flow to said motor to reverse the direction of operation thereof upon change of the contacts closed therein, said reversing switch means sending an electrical signal directly to said relay to change the contacts closed therein and thereby change the direction of rotation of said motor upon the encountering of an obstruction by the associated door, said motor remaining in closed circuit contact with said relay means during reveRsal of direction by operation of said reversing switch means, said disabling switch means opening the circuit for said reversing switch means to prevent generation of a signal thereby to said relay means when said drive means approaches the end of its preselected period of travel in said one direction.
 2. The electrical operator assembly of claim 1 wherein said relay means comprises a two-position relay having a member moveable between said two positions, a solenoid coil, and an armature acted upon by said solenoid coil to move said moveable member from one position to the other, said moveable member being latched in position until moved therefrom by action of said solenoid, and wherein said motor comprises a reversible motor having two windings and wherein the contacts of said relay in said positions thereof are each connected directly to one of said coils whereby the direction of rotation of said motor may be varied by changing the position of said relay, and wherein there is included means connecting said two windings of said motor to supply current 90* out of phase to the winding of said motor not directly receiving current through the contact of the relay in the operative position thereof.
 2. disabling switch means directly actuated by said said drive means after movement thereof for a preselected period of travel in one direction, said preselected period of travel being less than the preselected period of travel for the motor discontinuing limit switch means in that direction; and
 3. The electrical operator assembly of claim 2 wherein said limit switch means in said control circuitry comprises separate limit switches disposed in the circuits between the separate coils of said motor and said contacts of said relay in the two positions thereof, whereby opening of either of the limit switches in the closed circuit will discontinue flow of current to said motor and terminate operation of the assembly.
 3. multiposition relay means controlling current flow to said motor to reverse the direction of operation thereof upon change of the contacts closed therein, said reversing switch means sending an electrical signal directly to said relay to change the contacts closed therein and thereby change the direction of rotation of said motor upon the encountering of an obstruction by the associated door, said motor remaining in closed circuit contact with said relay means during reveRsal of direction by operation of said reversing switch means, said disabling switch means opening the circuit for said reversing switch means to prevent generation of a signal thereby to said relay means when said drive means approaches the end of its preselected period of travel in said one direction.
 4. The electrical operator assembly of claim 1 wherein said biasing means comprises a compression spring acting upon the opposite end portion thereof to bias said opposite end portion toward said belt member and threaded adjusting means to closely adjust the biasing force exerted thereby.
 5. The electrical operator assembly of claim 1 wherein said disabling switch means and said reversing switch means are in series with current flow to said reversing switch being through the disabling switch in its normally closed position, said disabling switch means opening to disable said reversing switch means.
 6. The electrical operator assembly of claim 1 wherein said drive means includes a shaft member having a threaded portion and a threaded member mounted thereon, said support including means to prevent rotation of said threaded member whereby rotation of said shaft will produce movement of said threaded member along the length thereof; and wherein said limit switch means is actuated by said threaded member during movement thereof to a preselected distance along the length of said threaded portion, wherein said limit switch means comprises a pair of limit switches, and wherein there are provided a pair of threaded members at spaced points along the length of said threaded portion each acting upon one of said pair of limit switches at either extreme of the preselected period of travel.
 7. The electrical operator assembly of claim 6 wherein said pair of limit switches and said disabling switch are mounted adjacent each other and each has an actuator arm, one of said threaded members acting upon the actuator arm of said disabling switch means shortly before acting upon the actuator arm of the limit switch in the same direction of travel. 